The present invention relates to vulcanized solid rubber, which is superior in its long-term compressive permanent strain; sealing efficiency; low-temperature characteristics; fatigue durability; processability such as kneadability, extrudability and shape-retaining property; and its appearance. The xe2x80x9csolid rubberxe2x80x9d means rubber having substantially no cell, and it is different from cellular rubber or sponge.
Most of vulcanized solid rubber used for applications such as a car have been produced by vulcanizing ethylene-xcex1-olefin-non-conjugated diene copolymer rubber superior in its heat resistance, weather resistance, processability and cost. However, such vulcanized solid rubber cannot satisfy the following requirements recently required for vulcanized solid rubber.
A problem such that a sound such as engine sound, wind-cutting sound around doors and creaking sound of tires comes into a room during high-speed run of a car, and a problem of rain-leaking depend largely upon sealing performance of doors and windows. Therefore, vulcanized solid rubber having much more superior sealing efficiency has been desired. Particularly, materials such as a door-sealing material, a window-sealing material and an engine mount are used under compressed conditions for a long period of time, and therefore, vulcanized solid rubber having little compressive permanent strain has been desired.
The compressive permanent strain can be improved by using such an ethylene-xcex1-olefin-non-conjugated diene copolymer rubber having a high Mooney viscosity as a blend of 100 parts by weight of the ethylene-xcex1-olefin-non-conjugated diene copolymer rubber and 20 parts by weight of an extender oil exceeds 100 of Mooney viscosity (ML1+4 (121xc2x0 C.)). However, vulcanized solid rubber obtained using such an ethylene-xcex1-olefin-non-conjugated diene copolymer rubber has problems of poor kneadability, formation of carbon aggregation lumps, surface roughening and edge cutting of extrusion molded products, and surface roughening of die molded products.
Further, it is important that car doors and car windows can be opened and shut smoothly in a wide temperature range of from a low temperature to a high temperature. Therefore, vulcanized solid rubber capable of maintaining sufficient flexibility in a wide temperature range has been desired.
An object of the present invention is to provide vulcanized solid rubber, which is superior in its long-term compressive permanent strain; sealing efficiency; low-temperature characteristics; fatigue durability; processability such as kneadability, extrudability and shape-retaining property; and its appearance.
The present inventors have undertaken extensive studies of vulcanized solid rubber. As a result, it has been fond that the above-mentioned object can be accomplished by using a combination of an ethylene-xcex1-olefin-non-conjugated diene copolymer having a high Mooney viscosity and an extender oil. Thereby, the present invention has been obtained.
The present invention provides vulcanized solid rubber, which comprises a vulcanized product of an oil-extended copolymer comprising:
(i) 100 parts by weight of an ethylene-xcex1-olefin-non-conjugated diene copolymer satisfying the following requirements (1) to (4), and
(ii) 10 to 90 parts by weight of an extender oil:
(1) a weight ratio of an ethylene unit to an xcex1-olefin unit in the ethylene-xcex1-olefin-non-conjugated diene copolymer is from 73/27 to 40/60,
(2) an iodine value of the ethylene-xcex1-olefin-non-conjugated diene copolymer is from 20 to 36,
(3) Mooney viscosity (ML1xe2x88x924 (121xc2x0 C.)) measured according to JIS-K-6300 of a blend containing 100 parts by weight of the ethylene-xcex1-olefin-non-conjugated diene copolymer and 20 parts by weight of an extender oil is from 100 to 180, and
(4) a ratio of weight average molecular chain length/number average molecular chain length measured by gel permeation chromatography of the ethylene-xcex1-olefin-non-conjugated diene copolymer is from 3 to 5.
Examples of the xcex1-olefin of the ethylene-xcex1-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer used in the present invention are propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene. Of these, propylene and 1-butene are preferred.
A weight ratio of an ethylene unit and an xcex1-olefin unit, namely, ethylene unit/xcex1-olefin unit, in said copolymer is from 73/27 to 40/60, and preferably from 67/33 to 45/55. Here, the xe2x80x9cunitxe2x80x9d means a polymerized monomer unit. For example, the xe2x80x9cethylene unitxe2x80x9d means a polymerized ethylene unit. When the ethylene unit exceeds 73 parts by weight, the vulcanized solid rubber obtained may extremely deteriorate its compressive permanent strain at a low temperature. When the ethylene unit is less than 40, dispersion of a reinforcing agent such as carbon black and inorganic fillers in the vulcanized solid rubber obtained may be insufficient, thereby roughening a surface of the solid rubber.
In the present invention, the xe2x80x9cnon-conjugated dienexe2x80x9d of said copolymer means not only a non-conjugated diene but also a non-conjugated polyene such as a non-conjugated triene. Examples of such compounds are linear non-conjugated dienes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene and 7-methyl-1,6-octadiene; cyclic non-conjugated dienes such as cyclohexadiene, dicyclopentadiene, methyltetraindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene and 6-chloromethyl-5-isopropenyl-2-norbornene; trienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene and 1,4,9-decatriene; 5-vinyl-2-norbornene; 5-(2-propenyl)-2-norbornene; 5-(3-butenyl)-2-norbornene; 5-(4-pentenyl)-2-norbornene; 5-(5-hexenyl)-2-norbornene; 5-(5-heptenyl)-2-norbornene; 5-(7-octenyl)-2-norbornene; 5-methylene-2-norbornene; 6,10-dimethyl-1,5,9-undecatriene; 5,9-dimethyl-1,4,8-decatriene; 4-ethylidene-8-methyl-1,7-nonadiene; 13-ethyl-9-methyl-1,9,12-pentadecatriene; 5,9,13-trimethyl-1,4,8,12-tetradecadiene; 8,14,16-trimethyl-1,7,14-hexadecatriene and 4-ethylidene-12-methyl-1,11-pentadecadiene. These compounds may be used singly or in combination of two or more. A preferred compound is 5-ethylidene-2-norbornene or dicyclopentadiene or a combination of both.
An iodine value of the ethylene-xcex1-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer is from 20 to 36, and preferably from 22 to 32. When the iodine value is less than 20, the vulcanized solid rubber obtained may deteriorate its compressive permanent strain, or decrease its vulcanization speed. In this regard, when a large amount of a vulcanization accelerator is used in order to increase the vulcanization speed, the vulcanized solid rubber obtained may have blooming. When the iodine value exceeds 36, flexibility of the vulcanized solid rubber obtained may be insufficient.
Mooney viscosity of the ethylene-xcex1-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer satisfies a requirement that Mooney viscosity (ML1+4 (121xc2x0 C.)) measured according to JIS-K-6300 of a blend containing 100 parts by weight of said copolymer and 20 parts by weight of an extender oil is from 100 to 180, and preferably from 110 to 170. Here, the reason why the Mooney viscosity is expressed not by the Mooney viscosity of said copolymer itself but by that of the above-mentioned blend is as follows. In measuring Mooney viscosity of a copolymer having Mooney viscosity as high as 200 or more, an inconvenience such as a slip occurs between a torque-detecting rotor and the copolymer. Occurrence of such an inconvenience is unavoidable from a structural viewpoint of a Mooney viscosity measurement apparatus. As a result, it may be difficult to measure an accurate Mooney viscosity. When the Mooney viscosity is less than 100, it may be difficult to obtain vulcanized solid rubber having little compressive permanent strain, or vulcanized solid rubber having good fatigue durability. When the Mooney viscosity exceeds 180, it may be difficult to obtain vulcanized solid rubber having little quality variations. Incidentally, it is desirable that Mooney viscosity of the copolymer itself exceeds 200.
A Q value, namely, weight average molecular chain length/number average molecular chain length, measured according to gel permeation chromatography of the ethylene-xcex1-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer is from 3 to 5, and preferably from 3 to 4. It is generally said that the Q value increases with increase of a molecular weight distribution, and as a result, kneadability and extrudability can be improved. Whereas, in the present invention, when the Q value exceeds 5, the molecular weight in a high molecular weight portion further increases to make insufficient dispersion of a reinforcing agent such as carbon black and inorganic fillers contained in the vulcanized solid rubber obtained. As a result, physical properties of the vulcanized solid rubber may deteriorate. When the Q value is less than 3, kneading workability in the production of the vulcanized solid rubber may deteriorate.
A process for producing the ethylene-xcex1-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer is not particularly limited. It can be produced by a conventional process using a conventional catalyst such as a titanium catalyst, a vanadium catalyst and a metallocene catalyst.
The xe2x80x9cextender oilxe2x80x9d used in the present invention means a petroleum softening agent conventionally used in the production of oil-extended rubber. Examples of the extender oil are paraffin, naphthene and aromatic extender oils obtained by purifying high boiling fractions of petroleum. These extender oils generally show a dynamic viscosity of from 5 to 35 mm2/s at 100xc2x0 C.
The oil-extended copolymer used in the present invention is produced by a process wherein the extender oil is blended with the ethylene-xcex1-olefin-non-conjugated copolymer during the production step thereof, not by a process wherein the ethylene-xcex1-olefin-non-conjugated diene copolymer is once produced, and thereafter blended with the extender oil. More specifically, it is produced by a process wherein the extender oil is blended with the ethylene-xcex1-olefin-non-conjugated diene copolymer dissolved in a solvent in the production step thereof. The reason therefor is that according to the latter process, it may result in failure to sufficiently blend the copolymer with the extender oil because of a high Mooney viscosity of the ethylene-xcex1-olefin-non-conjugated diene copolymer used in the present invention.
With respect to a blending proportion of the ethylene-xcex1-olefin-non-conjugated diene copolymer and the extender oil in the present invention, the extender oil is from 10 to 90 parts by weight, and preferably from 20 to 80 parts by weight, per 100 parts by weight of said copolymer. When the extender oil is less than 10 parts by weight, the vulcanized solid rubber obtained easily causes problems of poor kneadability, formation of carbon aggregation lumps, surface roughening and edge cutting of extrusion molded products, and surface roughening of die molded products. The present invention has solved these problems by combining the ethylene-xcex1-olefin-non-conjugated diene copolymer having a high Mooney viscosity and the extender oil. When the extender oil exceeds 90 parts by weight, a viscosity of the blend comprising said copolymer and the extender oil is too low to obtain sufficient dispersion of a reinforcing agent such as carbon black and inorganic fillers in the vulcanized solid rubber obtained. As a result, the vulcanized solid rubber may deteriorate its characteristics.
A process for producing the vulcanized solid rubber in accordance with the present invention comprises, for example, the steps of (i) kneading a blend comprising the oil-extended copolymer, a vulcanizing agent and, if necessary, the below-mentioned ingredient, with a conventional kneading machine such as an open roll mill, a Banbury mixer, a kneader and an extruder to obtain a kneaded product, and (ii) vulcanizing (cross-linking) the resulting kneaded product under heating.
Examples of the vulcanizing agent are sulfur; sulfur chloride; sulfur dichloride; 4,4xe2x80x2-dithiodimorpholine; morpholine disulfide: alkylphenol disulfide; tetramethylthiuram disulfide; selenium dimethyldithiocarbamate; and organic peroxides such as dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-(t-butylperoxy)hexyne-3, di-t-butylperoxide, di-t-butylperoxide-3,3,5-trimethylcyclohexane and t-butylhydroperoxide. Of these, preferred are sulfur, dicumyl peroxide, di-t-butylperoxide and t-butylperoxide-3,3,5-trimethylcyclohexane.
Sulfur is used in an amount of usually from 0.1 to 10 parts by weight, and preferably from 0.5 to 5 parts by weight, per 100 parts by weight of the ethylene-xcex1-olefin-non-conjugated diene copolymer. The organic peroxide is used in an amount of usually from 0.1 to 15 parts by weight, and preferably from 0.5 to 8 parts by weight, per 100 parts by weight of said copolymer.
The vulcanizing agent may be used, if necessary, in combination with a vulcanization accelerator and a vulcanization coagent. Examples of the vulcanization accelerator are N-cyclohexyl-2-benzothiazole-sufenamide, N-oxydiethylene-2-benzothiazole-sulfenamide, N,N-diisopropyl-2-benzothiazole-sulfenamide, 2-mercaptobenzothiazole, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, dibenzothiazyl-disulfide, diphenylguanidine, triphenylguanidine, di-o-tolylguanidine, o-tolyl-bi-guanide, diphenylguanidine-phthalate, an acetaldehyde-aniline reaction product, a butylaldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde ammonia, 2-mercaptoimidazoline, thiocarbaniride, diethylthiourea, dibutylthiourea, trimethylthiourea, di-o-tolylthiourea, tetramethylthiuram monosulfide, teramethylthiuram disulfide, teraethylthiuram disulfide, terabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide, zinc dimethyldithiocarbamate, zinc diethylthiocarbamate, zinc di-n-butylthiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithlocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, zinc dibutylxanthate and ethylenethiourea. The vulcanization accelerator is used in an amount of from 0.1 to 20 parts by weight, and preferably from 0.2 to 10 parts by weight, per 100 parts by weight of the ethylene-xcex1-olefin-non-conjugated diene copolymer.
Examples of the vulcanization coagent are metal oxides such as magnesium oxide and zinc oxide. Of these, preferred is zinc oxide. The vulcanization coagent is used usually in an amount of from 3 to 20 parts by weight per 100 parts by weight of the ethylene-xcex1-olefin-non-conjugated diene copolymer.
When peroxides are used as the vulcanizing agent, examples of cross-linking coagent are sulfur, quinonedioxime compounds such as p-quinonedioxime, polyethylene glycol dimethacrylate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, ethylene dimethacrylate and divinylbenzene.
In producing the vulcanized solid rubber using the oil-extended copolymer and the vulcanizing agent, if necessary, an ingredient such as plasticizers; fillers; resins such as, for example, polyethylene and polypropylene; and rubber such as ethylene-xcex1-olefin-non-conjugated diene copolymers other than that mentioned above and different rubber may be incorporated.
The plasticizers may be those conventionally used for rubber. Examples thereof are process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, vaseline, coal tar pitch, caster oil, linseed oil, factice, beeswax, ricinolic acid, palmitic acid, barium stearate, calcium stearate, zinc laurate, atactic polypropylene and cumarone indene resin. Of these, particularly preferred is process oil. The plasticizer is used in an amount of usually from 10 to 150 parts by weight, preferably from 30 to 150 parts by weight, and more preferably from 50 to 150 parts by weight, per 100 parts by weight of the ethylene-xcex1-olefin-non-conjugated diene copolymer. The amount can be determined from a viewpoint of flexibility of the vulcanized solid rubber obtained.
Examples of preferred fillers are carbon black such as SRF, GPF, FEF, HAF, ISAF, SAF, FT and MT, and inorganic fillers such as pulverized silicic acid, calcium carbonate, talc and clay, which are conventionally used for rubber.
The vulcanized solid rubber in accordance with the present invention can be used the most suitably for rubber vibration insulator such as an engine mount and a muffler hunger.